1. Field of the Invention
The present invention relates to a substrate processing apparatus for performing coating and developing processing for substrates such as semiconductor wafers or the like to fabricate semiconductors, and in more detail, relates to a substrate processing apparatus capable of controlling the temperature and humidity of air to be supplied to a resist coating processing unit and a developing processing unit.
2. Description of the Related Art
In the process of fabricating a semiconductor device, there is a series of processing steps of coating a semiconductor wafer which is a substrate to be processed with a photo-resist solution, reducing a circuit pattern or the like in size and exposing a photo-resist film by means of photolithography, and performing developing processing. These processing steps are extremely important to high integration of the semiconductor device.
In these processing steps, the semiconductor wafer which has undergone cleaning processing is first subjected to hydrophobic processing in an adhesion processing unit and cooled in a cooling processing unit, and thereafter a photo-resist film is formed by coating in a resist coating processing unit. The semiconductor wafer on which the photo-resist film is formed is subjected to pre-bake processing in a hot plate unit, cooled in a cooling processing unit, and then exposed in accordance with a predetermined pattern in an aligner. Subsequently, the exposed semiconductor wafer is subjected to post-exposure bake processing and cooled in a cooling processing unit, and a developing solution is applied and the exposed pattern is developed in a developing unit. Finally, the semiconductor wafer is subjected to post-bake processing in the hot plate unit.
Out of such a series of processing steps, the steps except exposure processing are performed by a resist coating and developing processing system into which these processing units are integrated.
In the aforesaid resist coating processing unit, the influence of temperature and humidity upon the precision of film thickness of a resist film formed after a resist solution is applied is large, and hence it is necessary to precisely control the temperature and humidity of air inside a cup in this coating processing unit.
In the developing processing unit, line width accuracy is greatly influenced by the temperature of a developing solution, and therefore it is required to precisely control the temperature of air inside a cup in the developing unit.
From these respects, conventionally, air of which the temperature and humidity are strictly controlled at predetermined values is supplied into the cups in the coating processing unit and the developing processing unit, and the control of temperature and humidity is performed integrally.
In a temperature and humidity controller used on this occasion, outside air (for example, a temperature of 23.degree. C., a relative humidity of 45%) outside the resist coating and developing processing system is taken into a cooler and cooled to a temperature (for example, 7.degree. C., 95% to 100%) not more than a dew-point temperature, then warmed to a predetermined temperature (for example, 23.degree. C.) by a warmer, and thereafter humidified by a humidifier and regulated at predetermined temperature and humidity (for example, 23.degree. C., 40% to 50%). The air regulated as above is then supplied to a coating processing unit (COT) and a developing processing unit (DEV) respectively.
The reason why after temporarily being cooled in the cooler, outside air is warmed by the warmer and humidified by the humidifier, and thereby the temperature and humidity thereof are regulated is that the regulation of the temperature and humidity of air to be supplied to the coating processing unit (COT) is required.
Namely, the relative humidity of air reaches almost 100% by temporarily cooling outside air to a temperature not more than the dew-point temperature by the cooler, but moisture contained in the air is removed (dehumidified) by condensing it into dewdrops, thereby reducing the absolute amount of moisture contained in unit volume of air, and thereafter the air is warmed to a predetermined temperature by the warmer and humidified to a predetermined humidity by the humidifier.
Accordingly, there is a problem that all the air taken in needs to be heated after being cooled temporarily, which causes a sudden rise in running cost for electric power consumption and the like.
Another problem is that there is the possibility that the temperature of air changes while the air reaches the coating processing unit even if the temperature and humidity are controlled as described above. Furthermore, equipment including such cooler, warmer, and humidifier as described above is necessary to control the temperature and humidity of air to be supplied to the coating processing unit, but there is a problem that such equipment needs to be simplified to the utmost to thereby hold down running costs for electric power consumption and the like.